improve exportconfirm

so that it doesn't jump around so much when changing height

src/ExportConfirm.jsx

@@ -31,7 +31,7 @@ const sheetStyle = {
   display: 'flex',
 };
 
-const boxStyle = { margin: '15px 15px 50px 15px', background: 'rgba(25, 25, 25, 0.6)', borderRadius: 10, padding: '10px 20px' };
+const boxStyle = { margin: '15px 15px 50px 15px', background: 'rgba(25, 25, 25, 0.6)', borderRadius: 10, padding: '10px 20px', minHeight: 450 };
 
 const outDirStyle = { background: 'rgb(193, 98, 0)', borderRadius: '.4em', padding: '0 .3em', wordBreak: 'break-all', cursor: 'pointer' };